1. Field of the Invention
This invention relates to an improvement of the screw fixing mechanism for eyeglasses parts, and more particularly to a clamp type screw loosening prevention mechanism for eyeglasses which prevents unwelcome loosening of the screwed part in glasses by an ingeneous design of the configulation of the female screw which enables the clamping of the threaded male screw rod at the end portion toward the center of the axis.
2. Description of the Related Art
As it is widely known, the screwed parts of eyeglasses are very easy to become loose. For example, hinge joint between the temple and front frame of eyeglasses are often repeatedly opened and closed when wearing the glasses in the morning or taking off the glasses at night, as well as when the normal glasses are folded and changed to the sunglasses when going out. Whenever the glasses are repeatedly taken on and off, the male screw which fastens the temple's hinge joint receives the effect of gradual loosening by the turn friction which accompanies opening and closing of the temple, thus becoming loose without becoming noticed to the extent that the screw almost come out of the knuckle of the hinge joint, or loosened to the point of being shaky by the gradual loosening from the incessant small vibration when traveling by an airplane or train.
Then, why was the screw fastening mechanism of the eyeglasses of the prior arts were easy to become loose? To search for the reason, it seems that the greatest cause of the problem is the lack of practical mechanism for preventing the loosening of the screw suitable for eyeglasses because all parts except the lenses of the eyeglasses worn on human face are thin and narrow, and the male screws capable of using for fastening and joining purpose were minute.
Of course, proposals has so far been made which attempts to prevent the loosening of the screw fastened portion. The large numbers of them depended on the complex combination of a number of tiny precision parts. Their cost was high because they had to fit tight in the three dimensional narrow space of the delicate configulation of parts of an eyeglasses frame. Moreover, the assembly process became extremely cumbersome and inefficient, and the appearence was not stylish without refinement. Therefore, according to the recent tastes of the eyeglasses market where fashonable, slim design was favored, such proposals were not welcome.
A simple kind of proposals relating to the screw loosening prevention mechanism existed, but it merely taught easy method of coating a part or whole of the threaded rod of male screw with synthetic resin material thereby increasing the friction resistance between the male and female screw thread in the screw tightened condition. The problem with this solution was that synthetic resin coating could easily be worn out where the short and thin tiny eyeglass screw's threded rod part is coated with such and where the screw joint is repeatedly opened and closed such as hinge joint connecting temple, resulting in the loosening of the screw.
Even where the screw is rarely moved, e.g. rim closing block which enfold the lense, if some reason arise so that the lense needs to be replaced, when the male screw is unscrewed the synthetic resin coating will be removed from the threaded rod and the screw cannot be reused necessitating a replacement.
The present invention was made in view of the above mentioned shortcomings of the prior arts' screw loosening prevention mechanism, and it is an object of this invention to provide a screw loosening prevention mechanism for eyeglasses parts which does not loosen unwittingly because the end portion of the male screw rod becomes firmly clamped and in immovable condition after having screwed on properly, and using a minute screw in only thin and narrow space obtainable for eyeglasses screw fixing parts, easily and efficiently process screw fixing of parts.
Another object of the present invention is to provide a screw loosening prevention mechanism for eyeglasses which has simple structure and a few parts, capable of manufacturing at a low cost.
Still another object of the present invention is to provide a screw loosening prevention mechanism which is structurally strong, highly durable, and fully capable of enduring heavy duty use and repeated screwing and unscrewing.
Further object of the present invention is to provide a screw loosening prevention mechanism for eyeglasses which contributes to the improvement of the eyeglasses design by blending into the thin and narrow eyeglasses screw fixing space and which is capable of doing the screw fixing easily.